“迟到"怎么办?Ruby 中的字符串插值 [英] How to do "late" string interpolation in Ruby

问题描述

>> string = '#{var}'
=> "\#{var}"

>> proc = Proc.new { |var| string }
=> #<Proc:0xb717a8c4@(pry):6>

>> proc.call(123)
=> "\#{var}"

不是我想要的.string 周围的双引号导致明显的未定义的局部变量.

Not really what I want. Double quotes around string result in the obvious undefined local variable.

推荐答案

虽然这是可能的，但如果不使用 eval，它不会按照您的预期工作，通常这是一个坏主意如果有替代方案.好消息是您有多种选择.

Although this is possible, it's not going to work how you intend here without having to use eval, and generally that's a bad idea if there's an alternative. The good news is you have several options.

最直接的是使用 sprintf 格式，使用 String#% 方法更容易:

The most straightforward is to use sprintf formatting which is made even easier with the String#% method:

string = '%s'

proc = Proc.new { |var| string % var }

proc.call(123)
# => "123"

这是一种非常可靠的方法，因为任何支持 .to_s 方法的方法都可以工作，并且如果它包含可执行代码，则不会导致 Universe 内爆.

This is a really reliable method as anything that supports the .to_s method will work and won't cause the universe to implode if it contains executable code.

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